1. Technical Field
This invention relates to a rescue device for safely lowering people from elevated locations. More specifically, a person harnessed to the device is lowered to the ground, for example from a high-rise building, by gradually unwinding a cable that is attached to the building on one end.
2. Prior Art
If a fire breaks out in a high-rise building, people can be trapped on floors above the range of the fire department rescue equipment. In such instances, there is a need for a device to lower a person from the upper floors of the building. The device must be simple so that it may be learned in an emergency. Such a device must be versatile so that it may be safely used by persons weighing from 50 pounds to 300 pounds. It is important that the device is jam proof and that the descent is controlled at a safe speed. It is preferable that a person using the device be lowered smoothly to the ground without unnerving stops and starts.
Ideally, an emergency descent device would be small enough for a person to pack in a suitcase for use in the event of a hotel fire. A small device also lends itself to being stored in suitable quantities in high-rise buildings.
The emergency descent device must be capable of being stored for use many years after initial installation.
Various winches and safety cable devices are known in the prior art for lowering a person from high-rise buildings. However, all of the prior art devices have suffered from certain deficiencies in their performance, especially when used as personal emergency descent devices.
A primary problem with prior art emergency descent devices is their inability to lower persons of different weight at a controlled, safe rate of speed. The amount of weight attached to prior art devices critically effected the rate of descent. In some prior art devices, as the weight of an object increased, the velocity of descent similarly increased. In other prior art devices, particularly those using a centrifugal clutch, as the weight of an object attached to the device increased, the clutch tended to either lock-up or grab intermittently.
One such device, distributed by Safe-T-Scape Inc. of Nevada, is a self-contained unit housing a spool of high tensile strength cable with a clip at one end of the cable and a harness attached to the unit. The Safe-T-Scape unit uses a centrifugal clutch for controlling the rate at which the cable is dispensed from the unit. One drawback of the Safe-T-Scape device is that no braking action occurs until the unit is rotating at a speed sufficient to engage the centrifugal clutch. When used to jump from a multi-story building, an initial fast descent can be quite frightful, making other persons similarly trapped hesistant to use their own device. Another drawback of the device is that if the user encounters a balcony or ledge on the way down, nothing in the unit would prevent it from continuing down, and striking the person using the device, or continuing its descent past the user creating slack in the steel cable which would suddenly snap taught when the user leaves the ledge or other obstacle subjecting the cable to dangerous stress which could cause it to break. The Safe-T-Scape unit and others like it also have a tendency to jam, especially when a heavy person attempts to use the device. Since a heavy person exerts a large amount of force on the cable, the strain on the clutch mechanism is increased and the clutch may actually lock-up leaving the person suspended in mid-air, perhaps many stories above the ground. When a person using the Safe-T-Scape device finally reaches the ground, they must immediately reach up to stop the descent of the emergency escape device since it can not stop itself.
Another type of emergency descent device is the "fall-stop" device sold by Emar S. A. of France. The fall-stop device is a workman's safety harness unit which is designed to be attached to a beam. The fall-stop device is primarily used in industrial applications where workmen are required to work in high places. In such applications, a workman can be trained to use the device and suitable beams are generally available for anchoring the unit. The fall-stop unit is not appropriate for use in emergency situations because it is not simple to set up and use and a suitable anchoring point would be difficult to locate in emergency situations such as a high-rise fire.
The fall-stop device is subject to some of the same disadvantages as the Safe-T-Scape unit. The fall-stop device uses a centrifugal brake mechanism in which brake shoes are adapted to bear upon a brake drum as a result of centrifugal force. The brake is not biased into engagement with the drum. Therefore, the device requires a certain initial descent velocity before effective braking action is developed. This results in initial acceleration of the user before brake engages. When a heavy person uses the device the initial shock of engaging the brake can cause the device to jam. If the fall-stop device is inverted and the cable is attached to the building while the device is carried by a user, it will be subject to the same disadvantages as the Safe-T-Scape device since it is not capable of stopping itself when the person using the device encounters a stationary object such as a balcony or the ground.
In the fall-stop device the brake drum is not an integral part of the spool which dispenses the cable and therefore the brake portion of the apparatus does not directly cooperate with the spool to control dispensing of the cable. The lack of direct cooperation between the brake and the spool makes the device subject to malfunction and failure. The braking force is applied on only one side of the cable spool which causes the forces on the spool to be unbalanced.
Each of the above noted problems encountered by prior art devices is solved by the present invention as will hereinafter be described.